Process for coating aluminum



. To all whom it may concern:

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No Drawing.

ish for, metallic articles and to improved methods and processes ofobtaining the same.

The principal object of my invention is to coat or plate a metallic obect quickly and inexpensively without the use of the usual electricalcurrent in such a way that the coating will be permanent andwear-resisting, and so that it maybe either polished for a clear lusterfinish oroxidized for the darker finishes as desired.

Another object is to obtain desirable metallic finishesin a minimum oftime and at a minimum of expense.

One of the principal objects of the invention is to provide a suitablemetallic coating or aluminum which may be either polished or oxidized asdesired.

Another object of the invention is to provide such permanent metallicfinishes by the bath or di method as contrasted with the longer and moreexpensive method of the electric current.

The difiiculties in plating aluminum have long been known and manyendeavors have been made to accomplish it, but so far, none of thesemethods has proven commercially successful, especially when applied tothe so-called commercial aluminum. The trouble seems to have been thatthe. alumi num quickly oxidizes and becomes coated sidera le time, fromtwenty to thirty min- .utes and longer, to form a coating; andthisobviating coating has not been rmanent due to the oxidizing film"underlying. it. In my process the coating is practically instantaneous,thus the oxidizing film referred to above.

" Oneof the most popular and satisfactory Application f l ed December 4,1919. Serial No. 342,515.

finishes is that known as the gun metal finish, which has usually beenobtained by a heat process which is long. and expensive. It is possiblewith this process, to obtain substantially instantaneously and veryinexpensively, the desired plating. When applied over aluminiun it makesa most desirable article. It is, therefore, one of the ob- I jects ofthe invention to overcome these dllllCllllIlBS in the treatment ofaluminum and other metals and to producen finished article that shallpossess the desired characteristics.

Briefly stated my process is as follows, although these steps may bealternated and changed without affecting the final results, thepreferred form only being described here by way of illustration. It willbe understood that the s'teps and their order may be departed fromwithout departing from the spirit of the invention as expressed in theclaims.

The aluminum article to be plated is first subjected to a cleansingoperation in order to thoroughly prepare the same, in order that thearticle may take on a substantial plating. In cleansing the aluminumarticle, it is first immersed in a solution of substantially one part ofsal soda to substantially thirty-two parts of water, by weight, thesolution being charged with a substantial steady currentof electricity,and the. article is maintained immersed ntil it is thoroughly cleansed.The fact is the electro-chem-i- .ca-l action of the solution rapidlycleanses the aluminum article in avery short time and renders thesurface thereof 1 more 'sus ceptible to a substantial permanent plating.After the article is cleansed, it is removed from the electrifiedcleansing solution and-is immersed in a bath of cdp er cyanide saturatedsolution which is sub ected to heat substantially one hundred. andninety degrees Fahrenheit, thus generating a galvanic ,ac-

tion which, due to the surface receiving its preparation from theelectro-chemical action, the aluminum article will take on a substantialpermanent plating. At the time of immersing the article in the copper ca nide saturated solution, the. time consume is. substantially one-ha1faminute, itdepend ing entirely on the of the article, and

durin this intro uced. V

- If desired'silver nitrate can be used instead ofthecopper cyanide. Thearticle can step, there is no outside current 1 immersed in anotherbath, a cold solution of liver of sulphur and leave it there aboutone-half minute. It takes longer in Winter than in summer. No electriccurrent is introduced. This sulphur solution oxidizes the copper coatingor other metal, as the case may be, turns it dark until it has theappearance of un metal. It produces a very beautiful finish of highluster of the desired color, and which needs notbe further polished orbuffed. The article is ready for use as it comes from the sulphursolution.

In the case of copper, the dark finish is a sulphide .of copper, thesulphur solution simply oxidizes the copper coating; there is nothingbut the base metal underneath.

Articles treated with this process receive highlysatisf actory results,particularly with aluminum.

From the foregoing description it will be seen that there has beenproduced, metallic articles with the desired finishes in a rapid,expeditious and inexpensive way.

After applying a layer of copper on the article, it isalsopossible toplate the copper layer with other metals, such as gold, silver, nickel,etc.

In employing the term sal soda in the foregoing specification it is tobe understood that I have in mind thesubstan'ce listed in U. S. OfficialPharmacopaeia as crude sodii carbonas monohydratus, and that inreferring to liver ofsulphur I mean the substance so referred to in thebook aforesaid and also referred to in said book, page 30, as crudepotassa sulphurata, the commori nomenclature of the art havin been usedthroughout the specification and claims for more ready understanding bythe ordinary person in the art of the particular substances underconsideration.

I claim:

1 A process for plating aluminum articles, first consisting in preparingthe article by immersing the same in a solution of substantially onepart sal soda and substantially thirty-two parts water, by weight,charging the solution with a substantial steady current of electricity,the electro-chemical action of the solution rapidly cleansing thealuminum article, rendering the surface thereof more susceptible to asubsequent substantial permanent plating, then removing the article fromthe electrified cleansing solution, and immersing it in a bath of coppercyanide saturated solution which is subjected to heat substantially onehundred and ninety degrees Fahrenheit, thereby generating a galvanicaction which, due to the surface having previously received itspreparation from the electro-chemical action, the aluminum article willtake on a substantial permanent plating.

2. A process for plating aluminum articles, first consisting inpreparing the article by immersing the same in a solution ofsubstantially one part sal soda and substantially thirty-two partswater, by weight," charging the solution with a substantial steadycurrent of electricity, the electro-chemical action of the solutionrapidly cleansing the aluminum 'article, rendering the surface thereofmore susceptible to a subsequent substantial permanent plating, andimmersing it in a bath of copper cyanide saturated solution which issubjected to heat substantially one hundred and ninety degreesFahrenheit, thereby generating a galvanic action which, due to thesurface having previously received its preparation from theelectrochemical action, the aluminum article will take on a substantialpermanent plating, removing the article from the cyanide solution'andsubjecting it to a polishing process to give the article a lusterfinish, and finally oxidizing the polished surface thereof.

In testimony whereof I have aflixed my signature, in resence of twowitnesses.

. T OMAS CHARLES COLE. 7

Witnesses:

HARRY H. STYLL, Anion G. HASKELL.

